Digital feed system for electronic antenna array

ABSTRACT

A scanning antenna array having plural antenna units and a digital feed system for reversibly energizing plural ones of said units in unison with groups of different fixed amplitude signals. The feed system includes fixed power dividers for generating (or receiving) the plural signals, and a multiple tier switching system for applying said different groups of signals to preselected groups of said units in a preselected or desired order.

United States Patet 1 1 1111 3,713,158

Burnham 1 Jan. 23, 1973 DIGITAL FEED SYSTEM FOR 3,568,207 3 1971 Boyneset a]. ..343/754 ELECTRONIC ANTENNA ARRAY 3,573,837 4/1971 Reindel..343/778 [75] Inventor: E. Bumham, Sliver Spnng PrimaryExaminer-Benjamin A. Borchelt Assistant Examiner-Denis H. McCabe [73]Assignee: Litton Systems, Inc., College Park, Attorney-Alfred B. Levineand Alan C. Rose [22] Filed: April 26, 1971 ABSTRACT [21] APP] No137,320 A scanning antenna array having plural antenna units and adigital feed system for reversibly energizing plu- 3 ral ones of saidunits in unison with groups of different [52] US. Cl. ..343/ 100 SA,343/854 fixed amplitude signals, The feed system includes fixed [5] Int.Cl. ..H0lq 3/26 power dividers for generating (or receiving) the plural[58] Field of Search ..343/ 100 SA, 854 signals, and a multiple tierswitching system for applying said difi'erent groups of signals topreselected 5 References Cited groups of said units in a preselected ordesired order.

UNITED STATES PATENTS 5 Claims, 2 Drawing Figures 3,276,018 9/1966Butler ..343/100 8 POSITION SELECT I TO B MATRIX DIRECTED SIGNAL l4PATENTEDJAH 23 I973 SHEET 1 UF 2 l0 l0 l0 If" I2 DIGITAL l3 FEED MATRIXDIRECTIVE 1' SIGNAL INVENTOR FRED E. BURNHAM BY lqfix ful ATTORNEYPATENTEDJAN23 1973 SHEET 2 BF 2 INVENTOR FREDEBURNHAM BY 4 Lem? 1 TO 8MATRIX DIRECTED SIGNAL POWER DIVIDER SELECT FIG. 2

8 POSITION 72 I ATTORNEY DIGITAL FEED SYSTEM FOR ELECTRONIC ANTENNAARRAY STATEMENT OF THE INVENTION This invention relates to scannableantenna arrays systems and is particularly concerned with such systemshaving digitally switchable corporate feed systems for scanning thearray in precise descrete narrow steps.

BACKGROUND AND SUMMARY OF THE INVENTION In an earlier application of thesame Assignee, filed on Dec. 28, 1970, Ser. No. 101,639, there isdisclosed an electronically scannable antenna system employing anantenna array and lens wherein plural feeds or antenna units areenergizable in unison with different amplitude signals to scan the beamin narrow spatial increments.

According to the present invention there is provided a digital feedsystem wherein a plurality of groups of different amplitude fixedsignals are produced or resolved by means of a network of fixed powerdividers, and a multiple tiered or cascaded network of switchingmatrices are employed to selectively apply each of the different groupsof signals or codes in unison to preselected groups of the antenna unitsto scan the beam in fixed increment steps. By automatically actuatingthe multitiered switches in a preselected sequence the beam may beprogressively displaced in equal spatial and timed steps along a givenaxis.

DESCRIPTION OF THE DRAWING FIG. 11 is a schematic view, in perspective,illustrating a preferred circular antenna array and digital feed system,and

FIG. 2 is a block diagram illustrating details of a preferred digitalfeed system according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, theantenna array in a preferred embodiment is comprised of a series ofantenna units equally spaced apart from one another in a circularconfiguration to scan a full 360 region in space, as is disclosed in theearlier patent application above referred to. Each of the antennaelements 10 may itself comprise a vertical array of elements forproducing a beam of given beam shape. Each of the units 10 is fed by alead 11 or coaxial cable which, in turn, receives its signal afterpassage through a Luneberg or geodesic lens 12. The function of lens 12is to so adjust the phase of plural signals energizing the antenna unitsso that when plural ones of said antenna are energized in unison, thearray produces a planar wavefront beam directed radially outwardly fromdifferent angular locations of the circular array.

The lens 12 is, in turn, energized by a plurality of signals derivedfrom a digital feed matrix 13. The lens 12 receives energization by acircular array of probes, corresponding in number and circulararrangement to the number and arrangement of antenna units 10 and thefunction of the feed matrix is produce the appropriate group of signalsand apply these in unison to the appropriate group of probes on the lens12 so as to circularly scan the beam in space. When the system functionsas a transmitter, the feed matrix is energized by a transmitter source14 and should the system function as a receiver, the feed matrix appliesthe directionally received signal to the receiver 14.

FIG. 2 schematically illustrates a preferred digital feed matrixaccording to the invention for producing eight groups or codes of fourdifferent amplitude signals each, and selectively applying each of thesegroups of signals in unison to groups of four different probes on thelens (or four antenna units of the array).

1n a preferred system the antenna array includes a total of 256 antennaunits 10 disposed in the circular array of FIG. 1 and a like number andarrangement of probes on lens 12.

It is desired to selectively energize these antenna units in groups offour antennas at a time; with each such group of four antennas beingsequentially energized by a total of eight groups of signals. Forexample, initially the antenna units 1, 2, 3, and 4 of the array aresequentially energized by the following groups of different amplitudesignals:

Following the energization of antenna units 1, 2, 3, 4 above, by thesegroups of different amplitude signals, the next sequence of four antennaunits of the array, numbers 2, 3, 4, and 5, are sequentially energizedby the same groups of signals in the same order. Following this, thenext following group of antenna units 3, 4, 5, and 6 are sequentiallyenergized in the same manner, and so forth.

As is disclosed in greater detail in the earlier application referredto, the sequential energization of each group of antennas by thedifferent groups of fixed amplitude signals serves to incrementallydisplace the beam emitted by the array in descrete steps about a full360 in space. In a preferred antenna system, the switching of one groupof signals to the next group serves to incrementally displace the beamfrom the same antennas by an angle of 0. 1 76.

Thus from each group of four antennas of the array the beam is preciselydisplaced in eight angular steps of 0.l76 each, and then the next fouradjoining antenna units are sequentially energized to displace the beamin the same manner from the next four antennas.

FIG. 2, shows a preferred feed system 13 for performing these functions.As shown there is provided eight fixed power dividers 16 to 23,inclusive, with each fixed power divider producing a different group orcode of four different amplitude signals on each of four output lines,and having a single input line 25'for receiving or transmitting power toand from an adjustable position switch 24. The adjustable eight positionswitch 24 selectively applies energy to (or receives energy from) anyone of the eight power dividers 16 to 23, inclusive; interconnectingthat selected power divider with the directive signal receiver or powersource 14.

For selecting any one of these eight groups or codes of signals, thereis provided four lower tier switching matrices 30 to 33, inclusive witheach having eight input lines and a single output line. As shown, thefirst left hand signal from power divider 16 is connected to an inputline leading to the first lower tier matrix 30; the second signal frompower divider 16 is connected to the second lower tier matrix 31; thethird signal from divider 16 to the third matrix 32 and so forth.Similarly each of the other power dividers has its output linesconnected to each matrix. All four of these lower tier matrices areganged together for common operation with input matrix 24. Accordinglywhen these lower tier matrices are switched to their first position, thefirst fixed power divider unit 16 is selected and is interconnected bymatrix 24 with the directive signal receiver or transmitter 14.Additionally the four descrete signal outputs of the first power divider16 are selected by the four lower tier matrices and applied at theoutput lines 34, 35, 36, and 37 of the lower tier switching matrices. Ina similar manner, in the second selected position of the lower tierswitching matrices, the four discrete outputs of the second powerdivider 17 are selected and applied at the four outputs 34 to 37 of thelower tier switching matrices, and the input to power divider 17 isinterconnected by matrix 24 to source 14.

As generally discussed above, in a preferred circular antenna arraysystem of FIG. 1, there is provided a total of 256 antenna units 10. Forselecting any four of such units at a time there is provided a series offour upper tier switching matrices 40, 41, 42, and 43. Each of the uppertier switching matrices has a single input line 44 to 47, inclusive, asshown, that is selectively connectable to any one of 64 output lines.The output lines of the first upper tier matrix 40 are each connected toevery fourth lens probe or antenna unit, such as antennas 1, 5, 9, 13,17, 21 and so forth; those of the second upper tier matrix 41 to thenext series of every fourth antenna unit, such as antennas 2, 6, 10, 14,18, and so forth; whereas those of the third and fourth upper tier units42 and 43 are likewise each connected to a different series of everyfourth antenna units. Accordingly by means of these four upper tiermatrices 40 to 43 any desired group of four different antenna units maybe selected from the 256 units of the array.

For example, presupposing all four upper switching units 40 to 43 areswitched to select their first left hand output line, then antenna units1, 2, 3, and 4 are each connected to the input lines 44, 45, 46, and 47,respectively. Should upper switching unit 40 then be actuated to itssecond position to select antenna unit 5, while not changing theprevious selection of switching units 41, 42, and 43; then the antennas5, 2, 3, and 4 are selected. In a similar manner by appropiatelyactuating each switching unit in succession, each succeeding group offour antennas may be selected as follows:

Antennas lIIv- (Actuate Switch 41) 5 6 3 4 (Actuate Switch 42) 5 6 7 4(Actuate Switch 43) 5 6 7 8 However, since the order or arrangement ofthe antenna units selected is varied by this mode of actuation of theupper switching units, and since it is desired to uniformly scan theantenna array in equal steps about a full 360 arc in space, a pluralityof pairs of intermediate switching units 49 to 56, inclusive, areprovided to interconnect the appropriate lower tier switches 30 to 33,inclusive, with the upper tier switches 40 to 43, inclusive.

As shown, each pair of intermediate switches, such as 49 and 50 comprisea pair of switch matrices having a single input line and four outputlines that are selectively connectable to the input line. The singleinput lines of the lowermost of the pairs of intermediate switches 49,51, 53, and 55 are each connected to the output line of a different oneof the lower tier matrices 30 to 33, inclusive, and the single line ofthe uppermost intermediate tier switches 50, 52, 54, and 56 are eachrespectively connected to the inlet line of a different one of the uppertier matrices 40 to 43, respectively. The remaining four lines of eachintermediate tier switch are so interconnected with each other switchmatrix of the pairs as to change the order of the four antennas selectedby the upper tier switches. Thus when the upper tier matrices selectantenna units 5, 2, 3, and 4 (in that order) as described above, theintermediate tier switches may change this order of energized antennaunits to 2, 3, 4, and 5 so that each of the groups or codes of signalsproduced by the power dividers 16 to 23 can be successively applied toeach succeeding four antenna units in a uniform order as follows:

Antenna Units 1 2 3 4 Antenna Units 2 3 4 5 Antenna Units 3 4 5 6Antenna Units 4 5 6 7 Antenna Units 5 6 7 8 Antenna Units etc.

It will be noted that all of the intermediate tier switches 49 to 56,inclusive, are ganged together for common actuation to four differentswitching positions, as indicated by the dotted line 71. In the firstswitching position of the intermediate tier matrices the outputs of eachof the four lower tier matrices 30 to 33 are connected to the input ofthat upper tier matrix that is directly above. For example, lower tiermatrix 30 is connected to upper tier matrix 40; lower 31 to upper 41;lower 32 to upper 42; and lower 33 to upper 43. In the second positionof intermediate tier switchs the output of matrix 30 is switched to theinput of upper 41; lower 31 to upper 42; lower 32 to upper 43; and lower33 to upper 40. In this manner when upper tier matrices select theantenna units in the order of 5, 2, 3, and 4, for example, theintermediate tier switches are actuated to their second position toenergize these selected antennas in the desired correct order ofantennas units 2, 3, 4, and 5. Similarly, when the upper tier matricesselect the next group of antennas in the order 5, 6, 3, and 4, theintermediate tier switches are actuated to their third position torearrange and energize the selected antennas in the desired order ofunits 3, 4, 5, and 6.

Consequently by means of the upper tier matrices and the intermediatetier switches, each succeeding group of four antennas, out of the entirearray of 256 antennas, may be selected in a desired regular succeedingorder; and by switching the lower tier matrices each of these regularlyselected groups of antennas may be successively energized in sequence byeight groups of fixed amplitude voltages to progressively scan theantenna beam in precise accurate steps.

Many variations may be made by those skilled in this art and thisinvention is accordingly to be considered as limited only by thefollowing claims.

What is claimed is:

l. A digital switching system for scanning antenna arrayscomprising: 7 7it 7 t a plurality of fixed power dividers arranged in given order, eachhaving plural output lines interconnected in differing preset powerdivision ratio to a common input,

a plurality of lower tier switching means for simultaneously selectingthe plural outputs of any of the fixed power dividers and applying theselected outputs to a like number of lower tier terminals in the sameorder,

a plurality of upper tier switching matrices, equal in number to thelower tier matrices, for selectively connecting plural antenna elementsof an array to a like number of upper terminals,

each upper tier switching matrices having a plurality of outputsconnected to different antenna elements than other matrices, and acommon input selectively connectable to any one of the outputs,

the adjoining outputs of each upper tier matrix being connected tononadjoining antenna elements of the array in arithmetical progression,with each upper tier matrix staggered in order of connection with apreceeding upper tier matrix,

and a plurality of intermediate tier matrices, equal in number to theupper tier matrices, for interconnecting the lower tier terminals andupper tier terminals and selectively interconnecting each lower terminalto any one of the upper terminals, thereby to interconnect the antennaelements of any selected group with the lower terminals in a desiredorder.

2. In the switching system of claim 1, at least two power dividers eachhaving at least two outputs, at least two lower tier matrices, at leasttwo upper tier matrices and at least two intermediate tier matrices;said antenna array having at least three elements and said multiple tiermatrices being actuable to sequentially interconnect the two outputsrofeach power divider to each adjoining pair of antenna elements in regularorder.

3. in the switching system of claim 1, eight power dividers, each havingfour outputs, four lower tier matrices, four upper tier matrices, andsaid antenna array having 256 elements.

4. In the switching system of claim 1, said lower tier switchingmatrices being interconnected for operation in unison and saidintermediate tier matrices being interconnected for operation in unison.

5. A digital feed system for interconnecting groups of antenna elementsof an array in unison successively with plural groups of power dividerscomprising:

a plurality of power dividers each having plural output lines providingdifferent ratios of power divisw iig ing means for selectivelyinterconnecting to the output lines of any divider, and antenna elementselecting switches for selecting any group of a plurality of adjoiningelements and applying these to the plural output lines of the selectedpower divider in regular order.

1. A digital switching system for scanning antenna arrays comprising: aplurality of fixed power dividers arranged in given order, each havingplural output lines interconnected in differing preset power divisionratio to a common input, a plurality of lower tier switching means forsimultaneously selecting the plural outputs of any of the fixed powerdividers and applying the selected outputs to a like number of lowertier terminals in the same order, a plurality of upper tier switchingmatrices, equal in number to the lower tier matrices, for selectivelyconnecting plural antenna elements of an array to a like number of upperterminals, each upper tier switching matrices having a plurality ofoutputs connected to different antenna elements than other matrices, anda common input selectively connectable to any one of the outputs, theadjoining outputs of each upper tier matrix being connected tononadjoining antenna elements of the array in arithmetical progression,with each upper tier matrix staggered in order of connection with apreceeding upper tier matrix, and a plurality of intermediate tiermatrices, equal in number to the upper tier matrices, forinterconnecting the lower tier terminals and upper tier terminals andselectively interconnecting each lower terminal to any one of the upperterminals, thereby to interconnect the antenna elements of any selectedgroup with the lower terminals in a desired order.
 2. In the switchingsystem of claim 1, at leAst two power dividers each having at least twooutputs, at least two lower tier matrices, at least two upper tiermatrices and at least two intermediate tier matrices; said antenna arrayhaving at least three elements and said multiple tier matrices beingactuable to sequentially interconnect the two outputs of each powerdivider to each adjoining pair of antenna elements in regular order. 3.In the switching system of claim 1, eight power dividers, each havingfour outputs, four lower tier matrices, four upper tier matrices, andsaid antenna array having 256 elements.
 4. In the switching system ofclaim 1, said lower tier switching matrices being interconnected foroperation in unison and said intermediate tier matrices beinginterconnected for operation in unison.
 5. A digital feed system forinterconnecting groups of antenna elements of an array in unisonsuccessively with plural groups of power dividers comprising: aplurality of power dividers each having plural output lines providingdifferent ratios of power division, switching means for selectivelyinterconnecting to the output lines of any divider, and antenna elementselecting switches for selecting any group of a plurality of adjoiningelements and applying these to the plural output lines of the selectedpower divider in regular order.